1. Field of the Invention
The present invention relates to a display device.
2. Description of the Related Art
A touch panel is configured to recognize a position on the touch panel touched by a pen or a finger and to use the positional information as an input signal for driving. A display device having such a touch panel has become popular because it does not need an external input device such as a keyboard or a mouse, and there has also been developed a liquid crystal display device incorporating a touch sensor in a liquid crystal panel (see, for example, Japanese Patent Application Laid-Open No. 2009-151138).
The inventors reviewed a display device structured to have a metal wiring (hereinafter, referred to as auxiliary wiring or light-blocking metal layer) in a region with the light blocked out by a black matrix in order to reduce resistance of a transparent electrode (ITO) used as a touch sensor wiring in a display device incorporating the touch sensor therein.
The display device reviewed by the inventors is described with reference to FIGS. 10A and 10B.
FIG. 10A is a plan view for illustrating a configuration of the display device in its display area. FIG. 10B is a cross-sectional view along a line A-A′ in FIG. 10A (some parts such as the black matrix are omitted in the plan view).
The display device 100 includes subpixels of red (R), green (G), blue (B), and white (W) in a vertical stripe shape, where RGB and RGW are respectively regarded as a single pixel, and the RGB pixels and the RGW pixels are arranged alternately. The number of each of B and W is half of that of R or G. The display device 100 includes a TFT substrate (array substrate) 101, a counter substrate 200, and a liquid crystal 300 arranged between the array substrate 101 and the counter substrate 200.
In the array substrate 101, a common electrode 120 is placed on a signal wiring (video signal line) 115 via an organic flattened film (HRC) 110. A pixel electrode 150 is placed on the common electrode 120 via an interlayer insulating film (an inorganic insulating film such as SiN) 140. The common electrode 120 extends in a direction parallel to a video signal line 115 (vertical direction in FIG. 10A) and is divided in a direction perpendicular to the video signal line 115 (lateral direction in FIG. 10A) by a common electrode slit portion 121 to be periodically arranged, and an auxiliary wiring 130 is arranged on the video signal line 115 in electrical contact with the common electrode 120. The auxiliary wiring 130 is arranged in a position overlapping a black matrix 210 as seen vertically from above between subpixels of different colors. In order that the divided common electrodes 120 may not short-circuit one another, however, the auxiliary wiring 130 is not arranged in the divided region (common electrode slit portion) 121 of the common electrode 120. The common electrode 120 and the pixel electrode 150 are formed of a translucent conductor film such as ITO (Indium Tin Oxide), and the auxiliary wiring 130 and the video signal line 115 are formed of a light-blocking conductor film (low-resistance conductor film, metal film).
The counter substrate 200 includes the black matrix (BM, light-blocking layer) 210 and RGBW color filters (colored layer) 220. The color filters 220 are arranged in the order of R, G, B, R, G, W in the extending direction of the video signal line 115 and the vertical direction (lateral direction in FIG. 10A) in the repeated manner. As for R and G color filters 220, those of the same color are aligned in the extending direction of the video signal line 115, whereas B and W filters are alternately arranged.
In the conventional display device without a touch sensor, a source metal wiring (signal wiring, video signal line) or the like is arranged on the array substrate side and the black matrix or the like is arranged on the counter substrate (CF substrate) side between subpixels of different colors, thereby blocking the light from an adjacent subpixel to prevent color mixture. However, as the high definition is developed, it is required to reduce the width of the metal wiring or the width of the black matrix, and the color mixture has been prevented by improving the effect of blocking the light from the adjacent subpixel by increasing the thickness of the metal wire, the thickness of the black matrix, or the both.
In the structure reviewed by the inventors, when the common electrode is not divided between adjacent subpixels as shown in FIGS. 7A and 7B, the auxiliary wiring (light-blocking metal layer) 130 is arranged in a position overlapping the black matrix 210 as seen vertically from above. Thus, the display device having this structure can use the auxiliary wiring (light-blocking metal layer) as a member for blocking the light from an adjacent subpixel. This point is explained with reference to FIG. 9A. FIG. 9A shows an exemplary case in which a blue filter 220B and a red filter 220R are adjacent to each other. When a light 410 that should pass through the blue filter 220B advances toward the adjacent red filter 220R, there can be a risk of color mixture. In such a case, by arranging the auxiliary wiring (light-blocking metal layer) 130, the light that would cause color mixture if there is no auxiliary wiring is blocked by the auxiliary wiring. Furthermore, it is possible to prevent color mixture because the light 410 having passed by the auxiliary wiring is blocked by the black matrix. Thus, the display device having the structure reviewed by the inventors is effective for prevention of color mixture. It should be noted that the reference numeral 411 denotes the light that is not able to pass therethrough but is blocked.
However, if higher definition is required for the display device and, for example, the width of the black matrix is reduced (width:t1>width:t2) in the future, there can be a risk of color mixture between the adjacent subpixels as shown in FIG. 9B. Such measures can be contemplated as to increase the thickness of the metal wiring as shown in FIG. 9C or to increase the thickness of the black matrix, but they may involve other issues that processing of the metal wiring and the black matrix should be time-consuming and cause side etching to make it difficult to obtain a desired shape.
Moreover, as shown in FIGS. 8A and 8B, it is required to provide the common electrode slit portion 121 for dividing the common electrode 120 used for the touch sensor, but the auxiliary wiring 130 cannot be arranged that has the same potential, which brings the risk of color mixture between the adjacent subpixels.
It is an object of the present invention to provide a display device inhibiting color mixture between the adjacent subpixels to obtain a high-quality image.